This is the ftp directory for GCC (GNU Compiler Collection).
Releases are in the releases/ directory, weekly snapshots of the
development sources are in the snapshots/ directory.
The GCC home page is
http://gcc.gnu.org
The GCC main ftp host is
ftp://gcc.gnu.org/pub/gcc
and http://gcc.gnu.org/mirrors.html has a list of mirror sites.
If you are going to download a snapshot, it would be a good idea to
join the main GCC developer mailing list, or to at least look over the
web archives of that mailing list.
If you want to be able to run the testsuites, then you will need a
recent copy of dejagnu. Look in the "infrastructure/" directory to
find one.
The mail-archives/ directory has archives of the GCC mailing lists,
split into months.